Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.81	10.796%	$157.1198	$157.12	$157.10	$157.10
Purchase #2	$127.38	13.411%	$144.4629	$144.46	$144.45	$144.50
Purchase #3	$85.86	12.776%	$96.8295	$96.83	$96.85	$96.80
Purchase #4	$229.46	13.554%	$260.561	$260.56	$260.55	$260.60
Purchase #5	$83.60	3.665%	$86.6639	$86.66	$86.65	$86.70
Purchase #6	$244.51	8.437%	$265.1393	$265.14	$265.15	$265.10
Purchase #7	$63.83	8.527%	$69.2728	$69.27	$69.25	$69.30
7 purchase totals =	$976.45		$1,080.0492	$1,080.04	$1,080.00	$1,080.10